Non-invasive optical analysis using surface enhanced raman spectroscopy

Abstract

In one aspect, a system for use in product packaging is disclosed that includes a polymeric sensing substrate coupled to a package such that a front sensing surface thereof is in contact with a portion of a product, e.g., a fungible product, stored in the package and a back surface thereof is accessible via an environment external to the package. The system further includes a radiation source adapted to direct radiation to the substrate's back surface such that the radiation would interact with one or more molecular species of the product that are in contact with the substrate's sensing surface. The system also includes a detector that is adapted to detect radiation returning from the substrate in response to its illumination by the radiation source. The front surface of the sensing substrate can comprise a plurality of micron-sized or submicron-sized ridges having a discontinuous or continuous metal coating, e.g., a metallic layer with a thickness in a range of about 10 nm to about 1000 nm (and preferably in a range of about 50 nm to about 120 nm), disposed thereon.

1. A system for use in product packaging, comprising
 a sensing substrate coupled to a package such that a front surface thereof is in contact with a portion of a product stored in said package and a back surface thereof is accessible to an environment external to the package, 
 a radiation source adapted to direct radiation to said back surface of the substrate, and 
 a detector adapted to detect radiation returning from said substrate in response to illumination by said radiation source. 
 
     
     
       2. The system of  claim 1 , wherein said product comprises a fungible product. 
     
     
       3. The system of  claim 1 , further comprising an analyzer operating on said detected radiation to determine a selected characteristic of said product stored in the package. 
     
     
       4. The system of  claim 3 , wherein said analyzer comprises a Raman spectrometer operating on said detected radiation to generate one or more Raman spectra of at least one constituent of said food product. 
     
     
       5. The system of  claim 4 , wherein said analyzer compares said one or more Raman spectra with one or more reference spectra to determine said selected characteristic. 
     
     
       6. The system of  claim 1 , wherein said front surface of the sensing substrate comprises a plurality of nano-sized ridges having a metallic coating disposed thereon. 
     
     
       7. The system of  claim 6 , wherein said metallic coating comprises a discontinuous metallic coating. 
     
     
       8. The system of  claim 6 , wherein said metallic coating comprises a substantially continuous metal layer. 
     
     
       9. The system of  claim 8 , wherein said metallic layer has a thickness in a range of about 10 nm to about 1000 nm. 
     
     
       10. The system of  claim 1 , further comprising an identification tag disposed on said package for identifying the product stored therein. 
     
     
       11. The system of  claim 10 , wherein said identification tag is optically readable. 
     
     
       12. The system of  claim 11 , wherein said identification tag comprises a bar code. 
     
     
       13. The system of  claim 3 , wherein said analyzer further comprises memory for storing said one or more reference spectra. 
     
     
       14. A method of non-invasively determining a characteristic of a product stored in a package, comprising
 coupling a polymeric sensing substrate to the package such that a sensing surface of said substrate is in contact with the product and an opposed surface of said substrate is accessible via an external environment, 
 directing radiation to said accessible surface from an external radiation source, 
 detecting at least a portion of radiation returning from the substrate in response to said radiation from the source. 
 
     
     
       15. The method of  claim 14 , wherein said detecting step comprises obtaining a surface enhanced Raman spectrum of at least one Raman active constituent of said product. 
     
     
       16. The method of  claim 14 , wherein said product comprises a fungible product. 
     
     
       17. The method of  claim 14 , wherein said opposed surface of the substrate is accessible to the external environment through a portion of the package. 
     
     
       18. An optical sensing system, comprising
 a chamber adapted for containing an analyte, 
 a polymeric substrate having a plurality of ridges and a metallic coating covering at least a portion of said ridges on a front side thereof, said substrate being coupled to the chamber such that at least a portion of said metallic coating is exposed to the chamber and at least a portion of the back side of the substrate is accessible via an external environment, 
 a radiation emitter optically coupled to said chamber so as to direct radiation to said accessible portion of the substrate back side, and 
 a detector coupled to the chamber and adapted to detect at least a portion of radiation returning from said substrate in response to illumination by said emitter. 
 
     
     
       19. The system of  claim 18 , wherein said emitter generates radiation for inducing a surface enhanced Raman scattering signal from at least one Raman active constituent of said analyte. 
     
     
       20. The system of  claim 19 , wherein said detector detects said Raman scattering signal. 
     
     
       21. The system of  claim 18 , wherein said metallic coating comprises a discontinuous metal coating.